The advent of tailored surgical instrumentation is related to present possibilities of acquiring sufficiently accurate pre-operative data in order to design from a dimensional point of view, instruments for which the interfaces for mechanical cooperation with the bones of the patient are specifically defined by taking into account the specific shape, notably the surface reliefs of these bones. The pre-operative data used typically stem from scanner images or more generally from any recording of bone mapping data advantageously obtained in a non-invasive way. These data are processed by a computer in order to control the manufacturing of tailored surgical instruments, once the surgeon has decided on the details of the surgical procedure which the surgeon will follow during a future operation.
During the operation, the surgeon positions on the bone a guiding block, including a shaped surface so as to specifically fit the bone of the patient. The guiding block then allows guidance of the application on the bone of a bone preparation tool, such as a boring bit or an anchoring pin. Subsequently, the guiding block has to be removed or moved away from the bone so as to allow the positioning of a cutting block. As the shape of the guiding block fitting the bone is relatively complex, this makes it difficult, or even impossible to remove the bone when the pins are inserted therein.